Methods for regulating gelation of hydrogel solutions and uses thereof

Abstract

The present invention provides a method for preparing chitosan and xylan composite thermo-gelling solutions to allow regulating the conditions in which the chitosan and xylan solution will gel. The present invention also provides methods for using chitosan/xylan solutions as compositions and for using chitosan/xylan solutions in vitro and in vivo. A thermally-responsive composite hydrogel has been developed and synthesized from the natural polymers chitosan and xylan. The new material is a viscous liquid at room temperature, but turns to a solid gel at physiological temperature (37 C). Rate of gelation is controlled with addition of a salt solution. Applications are for tissue engineering and local delivery of therapeutic agents, including proteins and drugs, as wells as cells.

What is claimed is: 
     
       1. A thermo-gelling solution comprising xylan, chitosan, a salt, and an acid, wherein when prepared said thermo-gelling solution is a solution at a pH between about 6.0 and about 8.0 and at a temperature below about 30° C., further wherein when the temperature is increased gelation of said solution occurs more rapidly or when the salt is added gelation occurs more rapidly, and wherein the ratio of chitosan to xylan is about 3 to 1 by weight. 
     
     
       2. The thermo-gelling solution of  claim 1 , wherein when said chitosan is 85% deacetylated ultrapure chitosan, the total amount of chitosan and xylan added is about 16 mg/ml. 
     
     
       3. The thermo-gelling solution of  claim 1 , wherein when said chitosan is 78.9% deacetylated ultrapure chitosan, the total amount of chitosan and xylan added is about 14.4 mg/ml. 
     
     
       4. The thermo-gelling solution of  claim 1 , wherein said gelation occurs within a temperature range from about 37° C. to about 50° C. 
     
     
       5. The thermo-gelling solution of  claim 4 , wherein said gelation occurs at about 37° C. 
     
     
       6. The thermo-gelling solution of  claim 1 , wherein said gelation occurs in less than about 1 hour when the temperature of said thermogelling solution is increased to about 37° C. 
     
     
       7. The thermo-gelling solution of  claim 6 , wherein said gelation occurs in less than about 30 minutes when the temperature of said thermogelling solution is increased to about 37° C. 
     
     
       8. The thermo-gelling solution of  claim 7 , wherein said gelation occurs in less than about 10 minutes when the temperature of said thermogelling solution is increased to about 37° C. 
     
     
       9. The thermo-gelling solution of  claim 8 , wherein said gelation occurs in less than about 5 minutes when the temperature of said thermogelling solution is increased to about 37° C. 
     
     
       10. The thermo-gelling solution of  claim 1 , wherein said salt is an inorganic salt. 
     
     
       11. The thermo-gelling solution of  claim 1 , wherein said salt is ammonium hydrogen phosphate or sodium pyruvate. 
     
     
       12. The thermo-gelling solution of  claim 11 , wherein when said salt is ammonium hydrogen phosphate, said solution comprises a ratio of chitosan to ammonium hydrogen phosphate between about 1.0 and about 3.5. 
     
     
       13. The thermo-gelling solution of  claim 11 , wherein when said salt is ammonium hydrogen phosphate, the concentration of said salt is about 20 mg/ml and the molarity of said salt is about 15 mmol/1. 
     
     
       14. The thermo-gelling solution of  claim 1 , wherein said solution further comprises an aqueous acidic solution. 
     
     
       15. The thermo-gelling solution of  claim 1 , wherein said solution comprises acetic acid at a concentration from about 0.25% v/v to about 0.5% v/v. 
     
     
       16. The thermo-gelling solution of  claim 1 , wherein said chitosan has a molecular weight of between about 20,000 and about 500,000. 
     
     
       17. The thermo-gelling solution of  claim 16 , wherein said chitosan has a molecular weight of about 429,000. 
     
     
       18. The thermo-gelling solution of  claim 1 , wherein said solution is biocompatible. 
     
     
       19. A pharmaceutical composition comprising the thermo-gelling solution of  claim 1 , a pharmaceutically-acceptable carrier, and optionally an effective amount of at least one cell, material, drug, therapeutic agent, or compound useful for treating an injury, disease, or disorder.